Vertical transmission of HIV-1 from infected mothers to their newborn infants occurs most frequently durng the time of delivery. Treatment of mothers during pregnancy, and labor and delivery, as well as post-birth treatment of the infant with zidovudine has reduced the risk of transmission of HIV-1 to the newborn from 25% to 8%. The addition of a single dose of a potent, long-acting antiretroviral agent, such as nevirapine, administered to the mother during labor and to the infant shortly after birth may potentially further decrease the risk of neonatal acquisition of HIV. The purpose of this study is to evaluate the effect of a single dose of nevirapine given to a mother during labor, in conjunction with a single dose of nevirapine given to the newborn, on the transmission of HIV-1 from infected mothers to their infants.